THE BASIS OF PLANT CLASSIFICATION 45 



The founder of the natural system, as something completely distinct 

 from artificial systems, was Antoine Laurent de Jussieu (1748- 1836), who 

 described and gave characters to a hundred families, nearly all of which are 

 still recognized. His uncle Bernard illustrated these ideas in laying out the 

 gardens of the Petit Trianon for Queen Marie Antoinette. 



From the principles laid down by de Jussieu systematic botany has never 

 departed. The work of the great nineteenth-century systematists was built 

 on his foundation, but it elaborated and extended the system as exploration 

 vastly increased our knowledge of plants. We should mention especially 

 John Lindley (1799-1865) (Fig. 25), who established Kew Gardens as a 

 national possession, and Sir Joseph Hooker (1817-1911) (Fig. 26), author of 

 a series of great Floras of the British Dominions, who, with George Bentham, 

 also set to work to rescue the genera of flowering plants from the confusion 

 into which they had fallen. Their work, the " Genera Plantarum," remains 

 the foundation work for all generic definitions. 



New versions of the natural system have appeared from time to time, 

 embodying current conceptions of affinity. Among the most notable we must 

 mention that of Adolf Engler which was embodied in his great work, edited 

 in collaboration with Prantl, " Die Natiirliche Pflanzenfamilien." 



It becomes invidious to attempt to select names from among the great 

 multitude who have contributed to build up modern knowledge of systematics, 

 and we can only cite a few whose work was of a fundamental nature. Py ramus 

 de CandoUe (1778-1841), who developed the principles of natural classification 

 in a series of classic monographs ; Robert Brown (1773- 1858) (Fig. 27), who 

 first separated the Gymnosperms as a group ; Asa Gray (1810-88), the great 

 systematist of the North ^American Flora ; and lastly a number of men, 

 each of whom was associated particularly with one of the groups of the lower 

 plants : Sir WilHam Hooker (1785-1865) with the Ferns ; C. H. Persoon 

 (1762-1836) and Elias Fries (1794-1878) with Fungi and Lichens ; P. A. 

 Saccardo (1845-1920), author of the monumental " Sylloge Fungorum " ; 

 J. Hedwig (1730-99) with the Bryophyta ; and W. H. Harvey (181 1-66), 

 K. H. Agardh (1785-1859) and de Toni (1864- 1924) with the Algae. 



It is impossible to follow developments into recent times, and, indeed, 

 it is worth comment that as science progresses the importance of personality 

 tends to fade into the background and to be replaced by the dominance of 

 theories which become the most influential factors in the advance of 

 knowledge. 



Principles of Classification 



We have referred above to the application by Linnaeus of the system of 

 binomial nomenclature. This consists of giving every organism two 

 names : a generic name and a specific name. The generic name is used 

 to describe forms which bear a general similarity to one another, for example, 

 the pear, the apple and the mountain ash are all placed in the same genus, 

 Pyrus. The specific name distinguishes the members of the genus from 



